Liquid crystal display device

Abstract

To provide a liquid crystal display device capable of preventing light leakage when a stress is exerted during no operation in a normally black IPS mode. In a normally black IPS mode liquid crystal display device 15, a liquid crystal layer 5 is interposed between a first glass substrate 1 and a second glass substrate 2, and a third glass substrate 3 is fixed to the second glass substrate 2. At that time, a retardation layer 7 to impart to a transmitted light a phase difference corresponding to a half-wavelength of the transmitted light, is provided between the second glass substrate 2 and the third glass substrate 3. Further, a first polarizing plate 8 and a second polarizing plate 9 are provided so that the respective absorption axes are perpendicular to each other.

1 . A liquid crystal display device comprising:
 a first transparent substrate,   a second transparent substrate,   a first adhesive to bond the first and second transparent substrates along their peripheral portions, and   a liquid crystal layer sealed between the first and second transparent substrates by the first and second transparent substrates and the first adhesive, wherein:   one of the first and second transparent substrates has, on its liquid crystal layer side, a common electrode set up commonly for respective pixels and a pixel electrode set up independently for every pixel, and   liquid crystal molecules in the liquid crystal layer are aligned in parallel to the first and second transparent substrates in such a state that no electric field is applied between the common electrode and each pixel electrode, and change their alignment direction in a plane parallel to the first and second transparent substrates when an electric field is applied in parallel to the first and second transparent substrates by the common electrode and the pixel electrode; and further comprising:   a third transparent substrate which is fixed by a second adhesive to the second transparent substrate on the side opposite to the liquid crystal layer, and   a retardation layer to impart to transmitted light a phase difference corresponding to a half wavelength of the transmitted light, between the second and third transparent substrates, wherein:   the first transparent substrate has a first polarizing plate on the side opposite to the liquid crystal layer, and   the third transparent substrate has a second polarizing plate on the side opposite to the retardation layer, so that the absorption axis is perpendicular to the absorption axis of the first polarizing plate.   
     
     
         2 . The liquid crystal display device according to  claim 1 , wherein the slow axis of the retardation layer is perpendicular or parallel to the alignment direction of liquid crystal molecules in the liquid crystal layer in such a state that no electric field is applied between the common electrode and each pixel electrode. 
     
     
         3 . The liquid crystal display device according to  claim 1 , wherein the slow axis of the retardation layer is parallel to the absorption axis of the second polarizing plate, and the alignment direction of liquid crystal molecules in the liquid crystal layer in such a state that no electric field is applied between the common electrode and each pixel electrode, is parallel to the absorption axis of the first polarizing plate. 
     
     
         4 . The liquid crystal display device according to  claim 1 , wherein the first and second transparent substrates have common thickness, Young's modulus and photoelastic coefficient, and when the thickness of the first and second transparent substrates is represented by d 1 , the Young's modulus of the first and second transparent substrates is represented by E 1 , the photoelastic coefficient of the first and second transparent substrates is represented by C 1 , the thickness of the third transparent substrate is represented by d 3 , the Young's modulus of the third transparent substrate is represented by E 3 , and the photoelastic coefficient of the third transparent substrate is represented by C 3 , the following formula is satisfied: 
       
         
           
             
               
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         5 . The liquid crystal display device according to  claim 1 , wherein an effective display region as a collection of regions of pixels corresponding to respective pixel electrodes, is rectangular,
 the second adhesive is disposed at least in a region outside of each side of the effective display region, and   the length of the second adhesive disposed along each side in the region outside of each side of the effective display region, is at least ½ of the length of the side of the effective display region corresponding to such a disposition position.   
     
     
         6 . The liquid crystal display device according to  claim 5 , wherein the second adhesive is transparent and is disposed to cover the effective display region between the transparent substrate provided with the retardation layer and the third transparent substrate. 
     
     
         7 . The liquid crystal display device according to  claim 1 , wherein the retardation layer is a half-wavelength plate. 
     
     
         8 . The liquid crystal display device according to  claim 1 , wherein the retardation layer is a second liquid crystal layer sealed by the second and third transparent substrates and the second adhesive, wherein the alignment direction of liquid crystal molecules is prescribed. 
     
     
         9 . The liquid crystal display device according to  claim 8 , wherein the second liquid crystal layer as the retardation layer is a liquid crystal layer made of the same material as the liquid crystal layer sealed between the first and second transparent substrates. 
     
     
         10 . The liquid crystal display device according to  claim 8 , wherein an inlet for the liquid crystal layer sealed between the first and second transparent substrates and an inlet for the second liquid crystal layer, are provided on the same side of the liquid crystal display device itself. 
     
     
         11 . The liquid crystal display device according to  claim 1 , wherein the second adhesive is photo-curable. 
     
     
         12 . The liquid crystal display device according to  claim 1 , wherein the second adhesive is an adhesive made of the same material as the first adhesive to bond the first and second transparent substrates along their peripheral portions. 
     
     
         13 . The liquid crystal display device according to  claim 1 , wherein the third transparent substrate is a touch panel having a transparent electrode on at least one side thereof. 
     
     
         14 . The liquid crystal display device according to  claim 1 , which has a transparent electrically-conductive layer between the third transparent substrate and the second polarizing plate. 
     
     
         15 . The liquid crystal display device according to  claim 1 , which has a biaxial retardation film between the third transparent substrate and the second polarizing plate, or between the first transparent substrate and the first polarizing plate, wherein:
 when the refractive index in a slow axis direction of the biaxial retardation film is represented by nx, the refractive index in a direction parallel to the main surface and perpendicular to the slow axis of the biaxial retardation film is represented by ny, and the refractive index in a thickness direction of the biaxial retardation film is represented by nz, nx>nz>ny is satisfied, and   the slow axis of the retardation layer is parallel to the alignment direction of liquid crystal molecules in the liquid crystal layer in such a state that no electric field is applied between the common electrode and each pixel electrode.   
     
     
         16 . A liquid crystal display device comprising:
 a first transparent substrate,   a second transparent substrate,   an adhesive to bond the first and second transparent substrates along their peripheral portions, and   a liquid crystal layer sealed between the first and second transparent substrates by the first and second transparent substrates and the adhesive, wherein:   one of the first and second transparent substrates has, on its liquid crystal layer side, a common electrode set up commonly for respective pixels and a pixel electrode set up independently for every pixel,   liquid crystal molecules in the liquid crystal layer are aligned in parallel to the first and second transparent substrates in such a state that no electric field is applied between the common electrode and each pixel electrode, and change their alignment direction in a plane parallel to the first and second transparent substrates when an electric field is applied in parallel to the first and second transparent substrates by the common electrode and the pixel electrode,   the first transparent substrate has a first polarizing plate, and   the second transparent substrate has a second polarizing plate so that the absorption axis is perpendicular to the absorption axis of the first polarizing plate; and further comprising:   a retardation layer to impart a phase difference to transmitted light, between at least one of the first and second transparent substrates, and the liquid crystal layer, wherein:   the sum of phase differences imparted to the transmitted light by the retardation layer is a phase difference of a half-wavelength of the transmitted light,   the alignment direction of liquid crystal molecules in the liquid crystal layer in such a state that no electric field is applied between the common electrode and each pixel electrode, is perpendicular to an absorption axis of one of the first and second polarizing plates, and   the slow axis of the retardation layer is perpendicular or parallel to the alignment direction of the liquid crystal molecules.   
     
     
         17 . The liquid crystal display device according to  claim 16 , wherein the retardation layer is one or more retardation films. 
     
     
         18 . The liquid crystal display device according to  claim 16 , which has an alignment layer to prescribe the alignment direction of liquid crystal molecules in the liquid crystal layer in such a state that no electric field is applied between the common electrode and each pixel electrode, as the uppermost layer on the liquid crystal layer side of each of the first and second transparent substrates. 
     
     
         19 . The liquid crystal display device according to  claim 18 , wherein the retardation layer is a half-wavelength plate,
 the half-wavelength plate is disposed between one of the first and second transparent substrates, and the liquid crystal layer, and   the alignment layer is formed on the surface in contact with the liquid crystal layer, of the half-wavelength plate.